Retuning method and apparatus

ABSTRACT

The present disclosure relates to retuning methods and apparatus. One example method includes determining a first resource and a second resource, where the first resource is used to receive a physical downlink control channel (PDCCH) or physical downlink shared channel (PDSCH), the first resource is determined based on a first frequency domain resource and M consecutive symbols of a downlink pilot timeslot in a special subframe, the second resource is used to send a sounding reference signal (SRS), the second resource is determined based on a second frequency domain resource and an uplink pilot timeslot in the special subframe, all or a part of the second frequency domain resource is not in the first frequency domain resource, and determining, in the last N consecutive symbols of the downlink pilot timeslot, a guard period for retuning.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/520,728, filed on Jul. 24, 2019, which is a continuation ofInternational Application No. PCT/CN2017/072504 filed on Jan. 24, 2017.All of the afore-mentioned patent applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

This application relates to the field of communications technologies,and in particular, to a retuning method and apparatus.

BACKGROUND

In a Long Term Evolution-Advanced (LTE-A) system, a base station needsto learn of wireless communication channel quality of user equipments(UE). Therefore, the base station schedules and instructs the UEs tosend sounding reference signals (SRS) to detect channels. The UEs sendthe SRSs. The base station estimates uplink channel quality of the UEsin different frequency bands by receiving and detecting the SRSs, toprovide a reference for resource block (RB) allocation, modulation andcoding, multi-antenna transmission parameter setting, and the like. SRSdetection has significant impact on performance of a wirelesscommunications system. Especially in a multi-antenna communicationssystem, SRS accuracy is critically related to downlink beamformingaccuracy.

An SRS may be sent in the last N symbols of a subframe. If the SRS issent in a normal subframe, a value of N is 1. If the SRS is sent in anUpPTS of a special subframe, a maximum value of N can be 6.

Currently, architectures of a further enhanced machine typecommunication (FeMTC) system and an enhanced machine type communicationeMTC) system are based on the LTE-A system. Bandwidth-reducedlow-complexity (BL) UE or coverage enhanced (CE) user equipment existsin the FeMTC system and the eMTC system. Uplink bandwidth supported bythese types of UEs may be less than system bandwidth. Therefore, an SRStransmission frequency band of UE may exceed uplink transmissionbandwidth of the UE. In the foregoing case, the UE needs to performretuning, to change a frequency domain position occupied by the UE totransmit an uplink resource, so as to transmit symbols in differentfrequency bands.

A time period needs to be occupied during retuning by the UE. The timeperiod may be referred to as a guard period. The UE cannot send a signalin the guard period. In addition, guard periods required for retuning bydifferent UEs depend on retuning capabilities of the UEs. A guard periodrequired by UE is usually {0. 1, 2} symbols. When the time periodrequired for retuning is 0 symbols, the UE can successfully send allSRSs and other uplink transmission signals. When the time periodrequired for retuning is one symbol or two symbols, the UE cannottransmit a signal or signals in one or two symbols during retuning. Inthe LTE-A system, when determining that an SRS transmission frequencyband exceeds uplink transmission bandwidth of UE so that retuning needsto be performed, the UE always preferentially uses a symbol occupied foran SRS as a guard period. In other words, no signal is sent in a timeperiod in which the SRS needs to be transmitted. However, considering aperformance requirement of the LTE-A system, SRS coverage needs to beenhanced. Therefore, the SRS needs to be repeatedly sent in a pluralityof symbols in time domain. If the UE does not preferentially transmitthe SRS during retuning, an SRS coverage enhancement requirement of theLTE-A system cannot be met.

SUMMARY

Embodiments of this application provide a retuning method and apparatus.During retuning by a terminal device, transmission of another signalless important than an SRS is preferentially dropped, to meet an SRScoverage enhancement requirement of a communications system.

According to a first aspect, an embodiment of this application providesa retuning method, including:

determining, by a terminal device, a first resource and a secondresource, where the first resource is used to send a sounding referencesignal, the first resource is determined based on a first frequencydomain resource and at least one symbol of a first subframe, and the atleast one symbol includes the last symbol of the first subframe; thesecond resource is used to send a physical uplink shared channel or aphysical uplink control channel, the second resource is determined basedon a second frequency domain resource and a second subframe, and all ora part of the first frequency domain resource is not in the secondfrequency domain resource; and the first subframe is the first subframein two consecutive subframes, and the second subframe is the secondsubframe in the two consecutive subframes; and

determining, by the terminal device in the first subframe and/or thesecond subframe, a guard period for retuning, where the guard period isused to forbid the terminal device to send an uplink signal in the guardperiod.

It should be noted that all or a part of the first frequency domainresource is not in the second frequency domain resource, or the firstfrequency domain resource does not fully overlap with the secondfrequency domain resource.

That the first frequency domain resource does not fully overlap with thesecond frequency domain resource means that no overlapping part existsbetween a subcarrier range within which the first frequency domainresource falls and a subcarrier range within which the second frequencydomain resource falls, or both an overlapping part and a non-overlappingpart exist between a subcarrier range within which the first frequencydomain resource falls and a subcarrier range within which the secondfrequency domain resource falls.

According to the foregoing design, in this embodiment of thisapplication, SRS sending is not preferentially dropped. Instead, theguard period for retuning is determined in the first subframe and/or thesecond subframe. This enhances SRS coverage based on terminal retuning.

Optionally, the terminal device determines, at least in the secondsubframe, the guard period for retuning. In the prior art, when a guardperiod is required for retuning, SRS sending is preferentially dropped.The last one or more symbols in symbols of the first subframe that areused to send the SRS are usually used as the guard period. In otherwords, the SRS and other uplink signals are forbidden to be sent in thelast one or more symbols of the first subframe. According to thesolution provided in this embodiment of this application, the SRS ispreferentially reserved instead of being preferentially dropped, andtransmission in the first one or more symbols of the second subframe arepreferentially dropped, so that the first one or more symbols of thesecond subframe are used as the guard period. This enhances SRScoverage.

In a possible design, the determining, by the terminal device in thefirst subframe and/or the second subframe, a guard period for retuningincludes:

determining, by the terminal device, that the guard period is in thefirst symbol in a plurality of symbols in the second subframe that areused to send the physical uplink shared channel or the physical uplinkcontrol channel.

According to the foregoing design, transmission of the physical uplinkshared channel or the physical uplink control channel in one symbol isdropped, to enhance SRS coverage with minimal impact on signaltransmission.

In a possible design, the determining, by the terminal device in thefirst subframe and/or the second subframe, a guard period for retuningincludes:

if the second resource is used to send the physical uplink controlchannel, determining, by the terminal device, that the guard period isin the last symbol of the first subframe and the first symbol in aplurality of symbols in the second subframe that are used to send thephysical uplink control channel.

According to the solution provided in this embodiment of thisapplication, when the first two symbols of the second subframe are usedto send the PUCCH, in an SRS coverage enhancement scenario, SRStransmission needs to be reserved as far as possible; in addition, asignal carried in the PUCCH is a control signal, and the control signalis of relatively high importance, and therefore PUCCH signaltransmission also needs to be reserved as far as possible. Therefore,transmission in one symbol selected from symbols used to transmit theSRS and transmission in one symbol selected from symbols used totransmit the PUCCH are dropped. Specifically, the terminal device usesthe last symbol of the first subframe and the first symbol of the secondsubframe as the guard period used to forbid the terminal device to sendan uplink signal. This enhances SRS coverage with minimal impact onsignal transmission.

In a possible design, the determining, by the terminal device in thefirst subframe and/or the second subframe, a guard period for retuningincludes:

if the second resource is used to send the physical uplink sharedchannel, determining, by the terminal device, that the guard period isin the first two symbols in a plurality of consecutive symbols in thesecond subframe that are used to send the physical uplink sharedchannel.

According to the foregoing design, when the first two symbols of thesecond subframe are used to send the PUSCH, in an SRS coverageenhancement scenario, SRS transmission needs to be reserved as far aspossible; in addition, a signal carried in the PUSCH is a data signal,and the data signal is of relatively low importance. Therefore, PUSCHtransmission in the first two symbols is chosen to be dropped.Specifically, the terminal device uses the first two symbols of thesecond subframe as the guard period used to forbid the terminal deviceto send an uplink signal. This enhances SRS coverage with minimal impacton signal transmission.

In a possible design, before the determining, by the terminal device inthe first subframe and/or the second subframe, a guard period forretuning, the method further includes:

receiving, by the terminal device, first indication information, wherethe first indication information is used to instruct the terminal deviceto determine the guard period in the first subframe and/or the secondsubframe.

In a possible design, the receiving, by the terminal device, firstindication information includes:

receiving, by the terminal device, radio resource control signaling,where the radio resource control signaling carries the first indicationinformation; or receiving, by the terminal device, downlink controlinformation, where the downlink control information includes the firstindication information.

According to the foregoing design, the indication information is carriedin higher layer signaling to indicate a manner in which the terminaldevice performs retuning, so that a symbol in which transmission needsto be reserved by the terminal device during retuning and a symbol inwhich transmission needs to be dropped by the terminal device duringretuning are flexibly selected. This improves flexibility.

In a possible design, before the determining a guard period in the firstsubframe and/or the second subframe, the method further includes:

receiving, by the terminal device, second indication information, where

the second indication information is used to indicate that the guardperiod is in the last symbol of the first subframe; or if the soundingreference signal is sent only in the last symbol of the first subframe,the second indication information is used to indicate that the guardperiod is in the last symbol of the first subframe and the first symbolof the second subframe; or if the sounding reference signal is sent onlyin at least two symbols of the first subframe, and the at least twosymbols include the last symbol of the first subframe, the secondindication information is used to indicate that the guard period is in aplurality of consecutive symbols from the first symbol to the lastsymbol in the at least two symbols of the first subframe.

In a possible design, the receiving, by the terminal device, secondindication information includes:

receiving, by the terminal device, radio resource control signaling,where the radio resource control signaling carries the second indicationinformation; or receiving, by the terminal device, downlink controlinformation, where the downlink control information includes the secondindication information.

According to the foregoing design, the indication information is carriedin higher layer signaling to indicate a manner in which the terminaldevice performs retuning, so that a symbol in which transmission needsto be reserved by the terminal device during retuning and a symbol inwhich transmission needs to be dropped by the terminal device duringretuning are flexibly selected. This improves flexibility.

In a possible design, bandwidth of the first frequency domain resourceis equal to transmission bandwidth of the sounding reference signal, andthe second frequency domain resource is a narrowband resource. Bandwidthof the narrowband resource is equal to maximum bandwidth that can besupported by the terminal device, or bandwidth of the narrowbandresource is equal to a maximum quantity of physical resource blocks thatcan be supported by the terminal device. The terminal device is abandwidth-reduced low-complexity (BL) terminal device, a coverageenhanced (CE) terminal device, or a machine type communication (MTC)terminal device.

The narrowband resource is described with respect to system bandwidth.When UE capabilities are limited, for example, costs are limited andpower consumption is limited, the second frequency domain resource maybe the narrowband resource. Supporting larger bandwidth requires highercosts and higher power consumption. Therefore, using the narrowbandresource can effectively reduce costs and total power consumption,improve transmit power in a unit frequency band to extend an uplinkcoverage area, and so on.

According to a second aspect, an embodiment of this application providesa retuning method, including:

determining, by a network device, a guard period for retuning from afirst resource to a second resource by a terminal device, where theguard period is in a first subframe and/or a second subframe, the guardperiod is used to forbid the terminal device to send an uplink signal inthe guard period, the first resource is used by the terminal device tosend a sounding reference signal, the first resource is determined basedon a first frequency domain resource and at least one symbol of thefirst subframe, and the at least one symbol includes the last symbol ofthe first subframe; the second resource is used by the terminal deviceto send a physical uplink control channel or a physical uplink sharedchannel, the second resource is determined based on a second frequencydomain resource and the second subframe, and all or a part of the firstfrequency domain resource is not in the second frequency domainresource; and the first subframe is the first subframe in twoconsecutive subframes, and the second subframe is the second subframe inthe two consecutive subframes; and

determining, by the network device, that no uplink signal of theterminal device exists in the guard period.

According to the foregoing design, in this embodiment of thisapplication, SRS sending is not preferentially dropped. Instead, theguard period for retuning is determined in the first subframe and/or thesecond subframe. This enhances SRS coverage based on terminal retuning.

Optionally, in a resource other than the guard period in the firstresource and the second resource, the network device monitors thesounding reference signal sent by the terminal device, and monitors thephysical uplink shared channel or the physical uplink control channelthat is sent by the terminal device.

In a possible design, the method further includes:

sending, by the network device, first indication information to theterminal device, where the first indication information is used toindicate that the guard period is in the first subframe and/or thesecond subframe.

According to the foregoing design, the indication information is used toindicate a manner in which the terminal device performs retuning, sothat a symbol in which transmission needs to be reserved by the terminaldevice during retuning and a symbol in which transmission needs to bedropped by the terminal device during retuning are flexibly selected.This improves flexibility.

In a possible design, the first indication information is used toindicate that the guard period is in the first symbol in a plurality ofconsecutive symbols in the second subframe that are used to send thephysical uplink shared channel or the physical uplink control channel.

According to the foregoing design, transmission of the physical uplinkshared channel or the physical uplink control channel in one symbol isdropped, to enhance SRS coverage with minimal impact on signaltransmission.

In a possible design, the first indication information is used toindicate that the guard period is in the last symbol of the firstsubframe and the first symbol in a plurality of symbols in the secondsubframe that are used by the terminal device to send the physicaluplink control channel.

According to the solution provided in this embodiment of thisapplication, when the first two symbols of the second subframe are usedto send the PUCCH, in an SRS coverage enhancement scenario, SRStransmission needs to be reserved as far as possible; in addition, asignal carried in the PUCCH is a control signal, and the control signalis of relatively high importance, and therefore PUCCH signaltransmission also needs to be reserved as far as possible. Therefore,transmission in one symbol selected from symbols used to transmit theSRS and transmission in one symbol selected from symbols used totransmit the PUCCH are dropped. Specifically, the terminal device usesthe last symbol of the first subframe and the first symbol of the secondsubframe as the guard period used to forbid the terminal device to sendan uplink signal. This enhances SRS coverage with minimal impact onsignal transmission.

In a possible design, the first indication information is used toindicate that the guard period is in the first two symbols in aplurality of symbols in the second subframe that are used by theterminal device to send the physical uplink shared channel.

According to the foregoing design, when the first two symbols of thesecond subframe are used to send the PUSCH, in an SRS coverageenhancement scenario, SRS transmission needs to be reserved as far aspossible; in addition, a signal carried in the PUSCH is a data signal,and the data signal is of relatively low importance. Therefore, PUSCHtransmission in the first two symbols is chosen to be dropped.Specifically, the terminal device uses the first two symbols of thesecond subframe as the guard period used to forbid the terminal deviceto send an uplink signal. This enhances SRS coverage with minimal impacton signal transmission.

In a possible design, the sending, by the network device, firstindication information to the terminal device includes:

sending, by the network device, radio resource control signaling to theterminal device, where the radio resource control signaling carries thefirst indication information; or sending, by the network device,downlink control information to the terminal device, where the downlinkcontrol information includes the first indication information.

According to the foregoing design, the indication information is carriedin higher layer signaling to indicate a manner in which the terminaldevice performs retuning, so that a symbol in which transmission needsto be reserved by the terminal device during retuning and a symbol inwhich transmission needs to be dropped by the terminal device duringretuning are flexibly selected. This improves flexibility.

In a possible design, the method further includes:

sending, by the network device, second indication information to theterminal device, where

the second indication information is used to instruct the terminaldevice to generate the guard period in the last symbol of the firstsubframe; or if the sounding reference signal is sent only in the lastsymbol of the first subframe, the second indication information is usedto indicate that the guard period is in the last symbol of the firstsubframe and the first symbol of the second subframe; or if the soundingreference signal is sent in at least two consecutive symbols of thefirst subframe, and the at least two consecutive symbols include thelast two symbols of the first subframe, the second indicationinformation is used to indicate that the guard period is in the last twosymbols of the first subframe.

In a possible design, the sending, by the network device, secondindication information to the terminal device includes:

sending, by the network device, radio resource control signaling to theterminal device, where the radio resource control signaling carries thesecond indication information; or sending, by the network device,downlink control information to the terminal device, where the downlinkcontrol information includes the second indication information.

According to a third aspect, based on a same inventive concept as themethod, an embodiment of this application provides a retuning apparatus,where the apparatus is applied to a terminal device and includes:

a first determining module, configured to determine a first resource anda second resource, where the first resource is used to send a soundingreference signal, the first resource is determined based on a firstfrequency domain resource and at least one symbol of a first subframe,and the at least one symbol includes the last symbol of the firstsubframe; the second resource is used to send a physical uplink sharedchannel or a physical uplink control channel, the second resource isdetermined based on a second frequency domain resource and a secondsubframe, and all or a part of the first frequency domain resource isnot in the second frequency domain resource; and the first subframe isthe first subframe in two consecutive subframes, and the second subframeis the second subframe in the two consecutive subframes; and

a second determining module, configured to determine, in the firstsubframe and/or the second subframe, a guard period for retuning, wherethe guard period is used to forbid the terminal device to send an uplinksignal in the guard period.

In a possible design, the second determining module is specificallyconfigured to determine that the guard period is in the first symbol ina plurality of symbols in the second subframe that are used to send thephysical uplink shared channel or the physical uplink control channel.

In a possible design, if the second resource is used to send thephysical uplink control channel, the second determining module isspecifically configured to determine that the guard period is in thelast symbol of the first subframe and the first symbol in a plurality ofsymbols in the second subframe that are used to send the physical uplinkcontrol channel.

In a possible design, if the second resource is used to send thephysical uplink shared channel, the second determining module isspecifically configured to determine that the guard period is in thefirst two symbols in a plurality of consecutive symbols in the secondsubframe that are used to send the physical uplink shared channel.

In a possible design, the apparatus further includes:

a receiving module, configured to receive first indication informationbefore the second determining module determines, in the first subframeand/or the second subframe, the guard period for retuning, where thefirst indication information is used to instruct the terminal device todetermine the guard period in the first subframe and/or the secondsubframe.

In a possible design, the receiving module is specifically configuredto:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the first indication information; or receivedownlink control information, where the downlink control informationincludes the first indication information.

In a possible design, the apparatus further includes:

a receiving module, configured to receive second indication informationbefore the second determining module determines the guard period in thefirst subframe andlor the second subframe, where

the second indication information is used to indicate that the guardperiod is in the last symbol of the first subframe; or if the soundingreference signal is sent only in the last symbol of the first subframe,the second indication information is used to indicate that the guardperiod is in the last symbol of the first subframe and the first symbolof the second subframe; or if the sounding reference signal is sent onlyin at least two symbols of the first subframe, and the at least twosymbols include the last symbol of the first subframe, the secondindication information is used to indicate that the guard period is in aplurality of consecutive symbols from the first symbol to the lastsymbol in the at least two symbols of the first subfrarne.

In a possible design, the receiving module is specifically configuredto:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the second indication information; or receivedownlink control information, where the downlink control informationincludes the second indication information.

In a possible design, bandwidth of the first frequency domain resourceis equal to transmission bandwidth of the sounding reference signal, andthe second frequency domain resource is a narrowband resource.

In a possible design, bandwidth of the narrowband resource is equal tomaximum bandwidth that can be supported by the terminal device, orbandwidth of the narrowband resource is equal to a maximum quantity ofphysical resource blocks that can be supported by the terminal device.

In a possible design, the terminal device is a bandwidth-reducedlow-complexity (BL) terminal device, a coverage enhanced (CE) terminaldevice, or a machine type communication (MTC) terminal device.

According to a fourth aspect, an embodiment of this application providesa retuning apparatus, where the apparatus is applied to a network deviceand includes:

a first determining module, configured to determine a guard period forretuning from a first resource to a second resource by a terminaldevice, where the guard period is in a first subframe and/or a secondsubframe, the guard period is used to forbid the terminal device to sendan uplink signal in the guard period, the first resource is used by theterminal device to send a sounding reference signal, the first resourceis determined based on a first frequency domain resource and at leastone symbol of the first subframe, and the at least one symbol includesthe last symbol of the first subframe; the second resource is used bythe terminal device to send a physical uplink control channel or aphysical uplink shared channel, the second resource is determined basedon a second frequency domain resource and the second subframe, and allor a part of the first frequency domain resource is not in the secondfrequency domain resource; and the first subframe is the first subframein two consecutive subframes, and the second subframe is the secondsubframe in the two consecutive subframes; and

a second determining module, configured to determine that no uplinksignal of the terminal device exists in the guard period.

In a possible design, the apparatus further includes:

a sending module, configured to send first indication information to theterminal device, where the first indication information is used toindicate that the guard period is in the first subframe and/or thesecond subframe.

In a possible design, the first indication information is used toindicate that the guard period is in the first symbol in a plurality ofconsecutive symbols in the second subframe that are used to send thephysical uplink shared channel or the physical uplink control channel.

In a possible design, the first indication information is used toindicate that the guard period is in the last symbol of the firstsubframe and the first symbol in a plurality of symbols in the secondsubframe that are used by the terminal device to send the physicaluplink control channel.

In a possible design, the first indication information is used toindicate that the guard period is in the first two symbols in aplurality of symbols in the second subframe that are used by theterminal device to send the physical uplink shared channel.

In a possible design, the sending module is specifically configured to:

send radio resource control signaling to the terminal device, where theradio resource control signaling carries the first indicationinformation; or send downlink control information to the terminaldevice, where the downlink control information includes the firstindication information.

In a possible design, the apparatus further includes:

a sending module, configured to send second indication information tothe terminal device, where

the second indication information is used to instruct the terminaldevice to generate the guard period in the last symbol of the firstsubframe; or if the sounding reference signal is sent only in the lastsymbol of the first subframe, the second indication information is usedto indicate that the guard period is in the last symbol of the firstsubframe and the first symbol of the second subframe; or if the soundingreference signal is sent in at least two consecutive symbols of thefirst subframe, and the at least two consecutive symbols include thelast two symbols of the first subframe, the second indicationinformation is used to indicate that the guard period is in the last twosymbols of the first subframe.

In a possible design, the sending module is specifically configured to:

send radio resource control signaling to the terminal device, where theradio resource control signaling carries the second indicationinformation; or send downlink control information to the terminaldevice, where the downlink control information includes the secondindication information.

According to a fifth aspect, an embodiment of this application providesa retuning method, including:

determining, by a terminal device, a first resource and a secondresource, where the first resource is used to receive a physicaldownlink control channel or a physical downlink shared channel, and thefirst resource is determined based on a first frequency domain resourceand M consecutive symbols of a downlink pilot timeslot in a specialsubframe; and the second resource is used to send a sounding referencesignal, the second resource is determined based on a second frequencydomain resource and an uplink pilot timeslot in the special subframe,and all or a part of the second frequency domain resource is not in thefirst frequency domain resource; and

determining, by the terminal device in the last N consecutive symbols ofthe downlink pilot timeslot or in the uplink pilot timeslot, a guardperiod for retuning, where the guard period is used to forbid theterminal device to transmit/receive a signal in the guard period, both Mand N are positive integers, and M is greater than or equal to N.

According to the foregoing design, the guard period for retuning isdetermined in the last N consecutive symbols of the downlink pilottimeslot or in the uplink pilot timeslot. A downlink control channel ora downlink shared channel transmitted in the downlink pilot timeslot isless important than the SRS that needs coverage enhancement. Therefore,reception of the downlink control channel or the downlink shared channelmay be chosen to be dropped or SRS transmission may be chosen to bedropped depending on a requirement, to improve flexibility and meet SRScoverage enhancement requirements of some terminal devices.

In a possible design, before the determining, by the terminal device inthe last N consecutive symbols of the downlink pilot timeslot, a guardperiod for retuning, the method further includes:

receiving, by the terminal device, first indication information, wherethe first indication information is used to instruct the terminal deviceto determine the guard period in the last N consecutive symbols of thedownlink pilot timeslot.

According to the foregoing design, the indication information is used toindicate a manner in which the terminal device performs retuning, sothat a symbol in which transmission needs to be reserved by the terminaldevice during retuning and a symbol in which transmission needs to bedropped by the terminal device during retuning are flexibly selected.This improves flexibility.

In a possible design, the receiving, by the terminal device, firstindication information includes:

receiving, by the terminal device, radio resource control signaling,where the radio resource control signaling carries the first indicationinformation; or receiving, by the terminal device, downlink controlinformation, where the downlink control information includes the firstindication information.

According to the foregoing design, the indication information is carriedin higher layer signaling to indicate a manner in which the terminaldevice performs retuning, so that a symbol in which transmission needsto be reserved by the terminal device during retuning and a symbol inwhich transmission needs to be dropped by the terminal device duringretuning are flexibly selected. This improves flexibility.

In a possible design, before the determining, by the terminal device inthe uplink pilot timeslot, a guard period for retuning, the methodfurther includes:

receiving, by the terminal device, second indication information, wherethe second indication information is used to indicate that the guardperiod is in the uplink pilot timeslot.

In a possible design, the receiving, by the terminal device, secondindication information includes:

receiving. by the terminal device, radio resource control signaling,where the radio resource control signaling carries the second indicationinformation: or receiving, by the terminal device, downlink controlinformation, where the downlink control information includes the secondindication information.

According to the foregoing design, the indication information is carriedin higher layer signaling to indicate a manner in which the terminaldevice performs retuning, so that a symbol in which transmission needsto be reserved by the terminal device during retuning and a symbol inwhich transmission needs to be dropped by the terminal device duringretuning are flexibly selected. This improves flexibility.

In a possible design, the first frequency domain resource is anarrowband resource, and bandwidth of the second frequency domainresource is equal to transmission bandwidth of the sounding referencesignal.

In a possible design, bandwidth of the narrowband resource is equal tomaximum bandwidth that can be supported by the terminal device, orbandwidth of the narrowband resource is equal to a maximum quantity ofphysical resource blocks that can he supported by the terminal device.

In a possible design, the terminal device is a bandwidth-reducedlow-complexity (BL) terminal device, a coverage enhanced (CE) terminaldevice, or a machine type communication (MTC) terminal device.

According to a sixth aspect, an embodiment of this application providesa retuning method, including:

determining, by a network device, a guard period for retuning from afirst resource to a second resource by a terminal device, where theguard period is in the last N consecutive symbols of a downlink pilottimeslot in a special subframe or the guard period is in an uplink pilottimeslot, and the guard period is used to forbid the terminal device totransmit/receive a signal in the guard period; the first resource isused to receive a physical downlink control channel or a physicaldownlink shared channel, and the first resource is determined based on afirst frequency domain resource and M consecutive symbols of thedownlink pilot timeslot; the second resource is used to send a soundingreference signal, the second resource is determined based on a secondfrequency domain resource and the uplink pilot timeslot in the specialsubframe, and all or a part of the second frequency domain resource isnot in the first frequency domain resource; and both M and N arepositive integers, and M is greater than or equal to N; and

determining, by the network device, that no signal of the terminaldevice exists in the guard period.

According to the foregoing design, the guard period for retuning isdetermined in the last N consecutive symbols of the downlink pilottimeslot or in the uplink pilot timeslot. A downlink control channel ora downlink shared channel transmitted in the downlink pilot timeslot isless important than the SRS that needs coverage enhancement. Therefore,reception of the downlink control channel or the downlink shared channelmay be chosen to be dropped or SRS transmission may be chosen to bedropped depending on a requirement, to improve flexibility and meet SRScoverage enhancement requirements of some terminal devices.

In a possible design, the method further includes:

sending, by the network device, indication information to the terminaldevice, where the indication information is used to indicate that theguard period is in the last N consecutive symbols of the downlink pilottimeslot or indicate that the guard period is in the uplink pilottimeslot.

In a possible design, the sending, by the network device, indicationinformation to the terminal device includes:

sending, by the network device, radio resource control signaling to theterminal device, where the radio resource control signaling carries theindication information; or sending, by the network device, downlinkcontrol information to the terminal device, where the downlink controlinformation includes the indication information.

According to the foregoing design, the indication information is carriedin higher layer signaling to indicate a manner in which the terminaldevice performs retuning, so that a symbol in which transmission needsto be reserved by the terminal device during retuning and a symbol inwhich transmission needs to be dropped by the terminal device duringretuning are flexibly selected. This improves flexibility.

According to a seventh aspect, an embodiment of this applicationprovides a retuning apparatus, where the apparatus is applied to aterminal device and includes:

a first determining module, configured to determine a first resource anda second resource, where the first resource is used to receive aphysical downlink control channel or a physical downlink shared channel,and the first resource is determined based on a first frequency domainresource and M consecutive symbols of a downlink pilot timeslot in aspecial subframe; and the second resource is used to send a soundingreference signal, the second resource is determined based on a secondfrequency domain resource and an uplink pilot timeslot in the specialsubframe, and all or a part of the second frequency domain resource isnot in the first frequency domain resource; and

a second determining module, configured to determine, in the last Nconsecutive symbols of the downlink pilot timeslot or in the uplinkpilot timeslot, a guard period for retuning, where the guard period isused to forbid the terminal device to transmit/receive a signal in theguard period, both M and N are positive integers, and M is greater thanor equal to N.

In a possible design, the apparatus further includes:

a receiving module, configured to receive first indication informationbefore the second determining module determines, in the last Nconsecutive symbols of the downlink pilot timeslot, the guard period forretuning, where the first indication information is used to instruct theterminal device to determine the guard period in the last N consecutivesymbols of the downlink pilot timeslot.

In a possible design, the receiving module is specifically configuredto:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the first indication information; or receivedownlink control information, where the downlink control informationincludes the first indication information.

In a possible design, the apparatus further includes:

a receiving module, configured to receive second indication informationbefore the second determining module determines, in the uplink pilottimeslot, the guard period for retuning, where

the second indication information is used to indicate that the guardperiod is in the uplink pilot timeslot.

In a possible design, the receiving module is specifically configuredto:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the second indication information; or receivedownlink control information, where the downlink control informationincludes the second indication information.

In a possible design, the first frequency domain resource is anarrowband resource, and bandwidth of the second frequency domainresource is equal to transmission bandwidth of the sounding referencesignal.

in a possible design, bandwidth of the narrowband resource is equal tomaximum bandwidth that can be supported by the terminal device, orbandwidth of the narrowband resource is equal to a maximum quantity ofphysical resource blocks that can be supported by the terminal device.

In a possible design, the terminal device is a bandwidth-reducedlow-complexity (BL) terminal device, a coverage enhanced (CE) terminaldevice, or a machine type communication (MTC) terminal device.

According to an eighth aspect, an embodiment of this applicationprovides a retuning apparatus, where the apparatus is applied to anetwork device and includes:

a first determining module, configured to determine a guard period forretuning from a first resource to a second resource by a terminaldevice, where the guard period is in the last N consecutive symbols of adownlink pilot timeslot in a special subframe or the guard period is inan uplink pilot timeslot, and the guard period is used to forbid theterminal device to transmit/receive a signal in the guard period; thefirst resource is used to receive a physical downlink control channel ora physical downlink shared channel, and the first resource is determinedbased on a first frequency domain resource and M consecutive symbols ofthe downlink pilot timeslot; the second resource is used to send asounding reference signal, the second resource is determined based on asecond frequency domain resource and the uplink pilot timeslot in thespecial subframe, and all or a part of the second frequency domainresource is not in the first frequency domain resource; and both M and Nare positive integers, and M is greater than or equal to N; and

a second determining module, configured to determine that no signal ofthe terminal device exists in the guard period.

In a possible design, the apparatus further includes:

a sending module, configured to send indication information to theterminal device, where the indication information is used to indicatethat the guard period is in the last N consecutive symbols of thedownlink pilot timeslot or indicate that the guard period is in theuplink pilot timeslot.

In a possible design, the sending module is specifically configured to:

send radio resource control signaling to the terminal device, where theradio resource control signaling carries the indication information; orsend downlink control information to the terminal device, where thedownlink control information includes the indication information.

According to a ninth aspect, an embodiment of this application furtherprovides a terminal device, where the terminal device includes atransceiver, a processor, and a memory, the transceiver is configured totransmit/receive data, the memory is used to store a software program,and the processor is configured to: read the software program stored inthe memory, and perform the method according to the first aspect or anyone of the designs in the first aspect, or perform the method accordingto the fifth aspect or any one of the designs in the fifth aspect.

According to a tenth aspect, an embodiment of this application providesa network device, where the network device includes a transceiver, aprocessor, and a memory, the transceiver is configured totransmit/receive data, the memory is configured to store a softwareprogram, and the processor is configured to: read the software programstored in the memory, and perform the method according to the secondaspect or any one of the designs in the second aspect, or perform themethod according to the sixth aspect or any one of the designs in thesixth aspect.

According to an eleventh aspect, an embodiment of this applicationfurther provides a computer storage medium, where the storage mediumstores a software program; and when the software program is read andexecuted by one or more processors, the method according to the firstaspect or any one of the designs in the first aspect, the methodaccording to the second aspect or any one of the designs in the secondaspect, the method according to the fifth aspect or any one of thedesigns in the fifth aspect, or the method according to the sixth aspector any one of the designs in the sixth aspect may be performed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a system architecture according to anembodiment of this application;

FIG. 2A is a schematic diagram of retuning corresponding to a scenario 1according to an embodiment of this application;

FIG. 2B is a schematic diagram of retuning corresponding to a scenario 2according to an embodiment of this application;

FIG. 3 is a flowchart of a retuning method in a scenario 1 according toan embodiment of this application;

FIG. 4 is a schematic diagram of retuning when B=1 in a scenario 1according to an embodiment of this application;

FIG. 5A and FIG. 5B are schematic diagrams of retuning when B=2 in ascenario 1 according to an embodiment of this application;

FIG. 6A and FIG. 6B are schematic diagrams of another type of retuningwhen B=2 in a scenario 1 according to an embodiment of this application;

FIG. 7A is a flowchart of another type of retuning in a scenario 1according to an embodiment of this application;

FIG. 7B is a flowchart of still another type of retuning in a scenario 1according to an embodiment of this application;

FIG. 8 is a schematic diagram of retuning based on indicationinformation in a scenario 1 according to an embodiment of thisapplication;

FIG. 9 is a flowchart of a retuning method in a scenario 2 according toan embodiment of this application;

FIG. 10 is a schematic diagram of retuning in a scenario 2 according toan embodiment of this application;

FIG. 11A and FIG. 11B are flowcharts of retuning methods in a scenario 2according to an embodiment of this application;

FIG. 12 is a schematic diagram of a retuning apparatus applied to aterminal device in a scenario 1 according to an embodiment of thisapplication;

FIG. 13 is a schematic diagram of a retuning apparatus applied to aterminal device in a scenario 2 according to an embodiment of thisapplication;

FIG. 14 is a schematic diagram of a terminal device according to anembodiment of this application;

FIG. 15 is a schematic diagram of a retuning apparatus applied to anetwork device in a scenario 1 according to an embodiment of thisapplication;

FIG. 16 is a schematic diagram of a retuning apparatus applied to anetwork device in a scenario 2 according to an embodiment of thisapplication; and

FIG. 17 is a schematic diagram of a network device according to anembodiment of this application.

DESCRIPTION OF EMBODIMENTS

The embodiments of this application may be applied to the 4th generationmobile communication (4G) system, for example, a Long Term Evolution(LTE) time division duplex (TDD) system, an LTE-A TDD system, or an eMTCor FeMTC system based on the LTE TDD system or the LTE-A TDD system, ormay be applied to the 5th generation mobile communication (5G) system,Alternatively, the embodiments of this application may be applied toanother communications system provided that an entity needs to transmita data signal and a reference signal to another entity in thecommunications system, for example, the communications system shown inFIG. 1.

As shown in FIG. 1, a base station (BS) and UE 1 to UE 6 constitute acommunications system. In the communications system, the base stationsends a scheduling message to one or more UEs in the UE 1 to the UE 6.In addition, UE 4 to UE 6 may also constitute a communications system.In the communications system, UE 5 may send scheduling information toone or more UEs in the UE 4 and the UE 6.

In addition, a terminal in the embodiments of this application may alsobe referred to as an access terminal, user equipment (UE), a subscriberunit, a mobile device, or the like. The terminal may be abandwidth-reduced low-complexity (BL) terminal, a coverage enhanced (CE)terminal, a machine type communication (MTC) terminal, or the like. Forease of description, the terminal is described as UE in thisapplication.

A network device in the embodiments of this application is an entityconfigured to receive or send a signal on a network side, for example, abase station. The base station may be a base transceiver station (BTS)in a Global System for Mobile Communications (GSM) or a Code DivisionMultiple Access (CDMA) system, may be a NodeB in a Wideband CodeDivision Multiple Access (WCDMA) system, or may be an evolved NodeB (eNBor eNodeB) in an LTE system, or a base station device, a small celldevice, a wireless access node (WiFi AP), a Worldwide Interoperabilityfor Microwave Access base station (WiMAX BS), or the like in a future SGnetwork. This is not limited in this application.

It should be noted that, “a plurality of” means “two or more” in thisapplication. The term “and/or” describes an association relationship fordescribing associated objects and represents that three relationshipsmay exist. For example, A and/or B may represent the following threecases: Only A exists, both A and B exist, and only B exists. Thecharacter “1” usually indicates an “or” relationship between theassociated objects. It should be understood that although terms “first”,“second”, “third”, and the like may be used in the embodiments of thisapplication to describe various symbols, the symbols are not limited bythe terms. These terms are merely used to distinguish between differentsymbols.

In addition, it should be noted that “guard period (guard period)” inthe embodiments of this application may also be referred to as a guardinterval. There are two types of guard periods. One type is a guardperiod for retuning (guard period for retuning) by UE. The other type isa guard period included in a special subframe. The guard period in thespecial subframe is used for switching from downlink transmission touplink transmission, to avoid interference caused by a downlink signalto an uplink signal. In the embodiments of this application, todistinguish between the two types of guard periods, in the followingdescription, the guard period for switching from downlink transmissionto uplink transmission is briefly referred to as a guard interval, andthe guard period for retuning by the UE is briefly referred to as aguard period.

A symbol in the embodiments of this application includes but is notlimited to an orthogonal frequency division multiplexing (OFDM) symbol,a sparse code multiple access (SCMA) symbol, a filtered orthogonalfrequency division multiplexing (F-OFDM) symbol, or a non-orthogonalmultiple access (NOMA) symbol, and may be specifically determineddepending on an actual situation. Details are not described herein.

With respect to a subframe in the embodiments of this application, onesubframe occupies a frequency domain resource of entire system bandwidthin frequency domain, and is a time domain resource of fixed duration intime domain. The subframe may include K symbols. A value of K may bedetermined depending on an actual situation, and is not limited herein.For example, in LTE, one subframe occupies 14 consecutive symbols intime domain; or in a 5G system, one subframe occupies 28/56 consecutivesymbols in time domain when a subcarrier width is 30 kHz/60 kHz,

Subframes may include an uplink subframe, a downlink subframe, and aspecial subframe. The uplink subframe is used to transmit an uplinksignal, and the downlink subframe is used to transmit a downlink signal.

The special subframe is divided in time domain. One special subframe maybe divided into three parts: a downlink pilot timeslot (DwPTS), a guardinterval (GP), and an uplink pilot timeslot (UpPTS).

The DwPTS is used for downlink transmission. No signal is transmitted inthe GP, and the GP is used for switching from downlink transmission touplink transmission, to avoid interference caused by a downlink signalto an uplink signal. The UpPTS is used for uplink transmission.

In a normal cyclic prefix (CP) configuration, the DwPTS, the GP, and theUpPTS include 14 symbols in total. In an extended CP configuration, theDwPTS, the GP, and the UpPTS include 12 symbols in total. Specifically,a quantity of symbols in the DwPTS, the GP, and the UpPTS is staticallyconfigured by the base station. The UpPTS may include a maximum of sixsymbols. For example, a possible configuration in a normal CP may be:DwPTS=3 symbols, GP=5 symbols, and UpPTS=6 symbols.

The following describes in detail scenarios in the embodiments of thisapplication.

An FeMTC system and an eMTC system are used as examples. A BL terminaldevice or a CE terminal device exists in the FeMTC system and the eMTCsystem. Uplink bandwidth supported by the foregoing types of terminaldevices may be less than system bandwidth. The system bandwidth may beconsidered as maximum total bandwidth that can be supported by acommunications system. An SRS transmission resource is scheduled by abase station, Therefore, after the scheduling by the base station, apart (or all) of SRS transmission bandwidth may not be in transmissionbandwidth supported by the terminal device, and therefore the terminaldevice needs to perform retuning, In one scenario, the terminal deviceperforms retuning in different subframes. In another scenario, theterminal device performs retuning in a special subframe.

Scenario 1: A terminal device performs retuning in different subframes.

As shown in FIG. 2A, a base station schedules a terminal device 1 totransmit an SRS in some frequency domain resources of the last twosymbols in a subframe n, and schedules the terminal device 1 to transmita physical uplink control channel (PUCCH) or a physical uplink sharedchannel (PUSCH) in the first two symbols in a subframe n+1, An uplinktransmission frequency domain resource that can be supported by theterminal device 1 is a frequency domain resource used to transmit thePUCCH or the PUSCH.

It can be seen from FIG. 2A that, the frequency domain resources fortransmitting the SRS exceed the frequency domain resource that can besupported by the terminal device 1. If a time period required forretuning by the terminal device is B =1 symbol (B indicates a quantityof symbols required for retuning by the terminal device), the terminaldevice needs to use one symbol as a guard period during retuning. Theterminal device does not send data in the guard period. If a time periodrequired for retuning is B=2 symbols, the terminal device needs to usetwo symbols as a guard period during retuning. Certainly, if 0 symbolsare required for retuning by the terminal device, during retuning, theterminal device can successfully send all SRSs and PUCCHs or PUSCHs thatneed to be sent. For example, the time period required for retuning bythe terminal device is one symbol. In an existing solution, an SRS isnot preferentially sent in any case, and therefore a guard period isgenerated in a symbol used to send the SRS. As shown in FIG. 2A, an SRSthat needs to be sent in the last symbol of the subframe n is not sent.

It should be noted that, in the scenario 1, the subframe n may be anuplink subframe or a special subframe. This is not specifically limitedin the embodiments of this application. The subframe n+1 may be anuplink subframe or a special subframe. This is not specifically limitedin the embodiments of this application.

Scenario 2: A terminal device performs retuning in a special subframe.

An SRS may be transmitted in an UpPTS of the special subframe, and canbe transmitted in a maximum of six symbols of the UpPTS. However, duringscheduling by a base station, SRS transmission bandwidth of the terminaldevice in an UpPTS of a special subframe may exceed downlinktransmission bandwidth of the terminal device in a DwPTS of the specialsubframe. As shown in FIG. 213, a base station schedules a terminaldevice 1 to transmit an SRS in some frequency domain resources of thelast two symbols in an UpPTS of a special subframe and to receive aPDCCH or receive a PDSCH in a DwPTS of the special subframe. Thefrequency domain resources used by the terminal device to send the SRSare completely or partly different from a frequency domain resource usedby the terminal device to receive the PDCCH or the PDSCH, and thereforea transmission frequency hand of the SRS is not in a downlinktransmission frequency band of the terminal device 1. In this case, theterminal device needs to perform retuning, to change a frequency domainresource position in which the terminal device transmits a signal, so asto transmit symbols in different frequency hands. For example, a timeperiod required for retuning by the terminal device is one symbol. In anexisting solution, an SRS is not preferentially sent in any case, andtherefore a guard period is generated in a symbol used to send the SRS.As shown in FIG, 2B, an SRS that needs to be transmitted by the terminaldevice in the UpPTS is not sent.

However, considering a performance requirement of a communicationssystem, SRS coverage needs to be enhanced. Therefore, the SRS needs tohe repeatedly sent in a plurality of symbols in time domain. If theterminal device does not preferentially transmit the SRS duringretuning, an SRS coverage enhancement requirement of the communicationssystem cannot be met.

Based on this, the embodiments of this application provide a retuningmethod and apparatus. During retuning by a terminal device, transmissionof another signal less important than an SRS is preferentially dropped,to meet an SRS coverage enhancement requirement of a communicationssystem, The method and apparatus are based on a same inventive concept.Because a problem-resolving principle of the method is similar to thatof the apparatus, mutual reference may be made between apparatusimplementation and method implementation. No repeated description isprovided.

The following describes in detail solutions provided in the embodimentsof this application with reference to the accompanying drawings.

Based on the scenario 1, an embodiment of this application provides aretuning method. As shown in FIG. 3, the method includes the followingsteps.

S301. A terminal device determines a first resource and a secondresource.

The first resource is used to send a sounding reference signal. Thefirst resource is determined based on a first frequency domain resourceand at least one symbol of a first subframe. The at least one symbolincludes the last symbol of the first subframe. The second resource isused to send a physical uplink shared channel or a physical uplinkcontrol channel. The second resource is determined based on a secondfrequency domain resource and a second subframe. The first subframe isthe first subframe in two consecutive subframes. The second subframe isthe second subframe in the two consecutive subframes.

It should be noted that all or a part of the first frequency domainresource is not in the second frequency domain resource, or the firstfrequency domain resource does not fully overlap with the secondfrequency domain resource.

That the first frequency domain resource does not fully overlap with thesecond frequency domain resource means that no overlapping part existsbetween a subcarrier range within which the first frequency domainresource falls and a subcarrier range within which the second frequencydomain resource falls, or both an overlapping part and a non-overlappingpart exist between a subcarrier range within which the first frequencydomain resource falls and a subcarrier range within which the secondfrequency domain resource falls.

S302. The terminal device determines, in the first subframe and/or thesecond subframe, a guard period for retuning, where the guard period isused to forbid the terminal device to send an uplink signal in the guardperiod.

Optionally, the terminal device determines, in the first subframe and/orthe second subframe based on a retuning capability of the terminaldevice, the guard period for retuning. The retuning capability of theterminal device may be specifically a quantity of symbols required forretuning by the terminal device.

In this embodiment of this application, bandwidth of the first frequencydomain resource is equal to transmission bandwidth of the soundingreference signal, and the second frequency domain resource may be anarrowband resource. Bandwidth of the narrowband resource is equal tomaximum bandwidth that can be supported by the terminal device, orbandwidth of the narrowband resource is equal to a maximum quantity ofphysical resource blocks that can be supported by the terminal device.

The narrowband resource is described with respect to system bandwidth.When UE capabilities are limited, for example, costs are limited andpower consumption is limited, the second frequency domain resource maybe the narrowband resource. Supporting larger bandwidth requires highercosts and higher power consumption. Therefore, using the narrowbandresource can effectively reduce costs and total power consumption,improve transmit power in a unit frequency band to extend an uplinkcoverage area, and so on.

In a possible implementation, the terminal device determines, at leastin the second subframe, the guard period for retuning. In the prior art,when a guard period is required for retuning, SRS sending ispreferentially dropped. The last one or more symbols in symbols of thefirst subframe that are used to send the SRS are usually used as theguard period. In other words, the SRS and other uplink signals areforbidden to be sent in the last one or more symbols of the firstsubframe. According to the solution provided in this embodiment of thisapplication, the SRS is preferentially reserved instead of beingpreferentially dropped, and the first one or more symbols of the secondsubframe are preferentially dropped and used as the guard period.

Optionally, when one symbol needs to be used as the guard period forretuning by the terminal device, in step S302, that the terminal devicedetermines, in the first subframe and/or the second subframe, a guardperiod for retuning may be specifically implemented in the followingmanner:

The terminal device determines that the guard period is in the firstsymbol in a plurality of symbols in the second subframe that are used tosend the PUSCH or the PUCCH.

It should be noted that if the PUCCH or the PUSCH is sent in the secondsubframe, the sending usually starts from the first symbol of the secondsubframe.

Specifically, the terminal device determines, based on the retuningcapability of the terminal device, that one symbol is required forretuning, and therefore the terminal device uses the first symbol of thesecond subframe as the guard period for retuning. In other words, theterminal device is forbidden to send an uplink signal in the firstsymbol of the second subframe.

For example, as shown in FIG. 2A, the first subframe is the subframe nin FIG. 2A, and the second subframe is the subframe n+1 in FIG. 2A. Inthe foregoing manner, one symbol needs to be used as the guard periodfor retuning by the terminal device, and therefore the terminal deviceuses the first symbol of the subframe n+1 as the guard period used toforbid the terminal device to send an uplink signal in the first symbolof the subframe n+1. For details after adjustment, refer to FIG. 4.

Optionally, when two symbols need to be used as the guard period forretuning by the terminal device, in step S302, that the terminal devicedetermines, in the first subframe and/or the second subframe, a guardperiod for retuning may be specifically implemented in the followingmanner:

If the second resource is used to send the PUCCH, the terminal devicedetermines that the guard period is in the last symbol of the firstsubframe and the first symbol in a plurality of symbols in the secondsubframe that are used to send the PUCCH.

For example, as shown in FIG. 5A and FIG. 5B, the first subframe is asubframe n in FIG. 5A and FIG. 5B, and the second subframe is a subframen+1 in FIG. 5A and FIG. 5B. The SRS is sent in the last two symbols ofthe subframe n. Because two symbols are required for retuning by theterminal device, according to a solution provided in the prior art, asshown in FIG. 5A, the terminal device sends no uplink signal in the lasttwo symbols of the subframe n. In other words, the last two symbols ofthe subframe n are used as the guard period. According to the solutionprovided in this embodiment of this application, as shown in FIG, 5B,when the first two symbols of the subframe n+1 are used to send thePUCCH, in an SRS coverage enhancement scenario, SRS transmission needsto be reserved as far as possible; in addition, a signal carried in thePUCCH is a control signal, and the control signal is of relatively highimportance, and therefore PUCCH signal transmission also needs to bereserved as far as possible. Therefore, transmission in one symbolselected from symbols used to transmit the SRS and transmission in onesymbol selected from symbols used to transmit the PUCCH are dropped.Specifically, the terminal device uses the last symbol of the subframe nand the first symbol of the subframe n+i as the guard period used toforbid the terminal device to send an uplink signal.

Optionally, when two symbols need to be used as the guard period forretuning by the terminal device, in step S302, that the terminal devicedetermines, in the first subframe and/or the second subframe, a guardperiod for retuning may be specifically implemented in the followingmanner:

If the second resource is used to send the physical uplink sharedchannel, the terminal device determines that the guard period is in thefirst two symbols in a plurality of consecutive symbols in the secondsubframe that are used to send the PUSCH.

For example, as shown in FIG. 6A and FIG. 6B, the first subframe is asubframe n in FIG. 6A and 6B, and the second subframe is a subframe n+1in FIG. 6.A and FIG. 6B. The SRS is sent in the last two symbols of thesubframe n. Because two symbols are required for retuning by theterminal device, according to a solution provided in the prior art, asshown in FIG. 6A, the terminal device sends no uplink signal in the lasttwo symbols of the subframe n. In other words, the last two symbols ofthe subframe n are used as the guard period. According to the solutionprovided in this embodiment of this application, as shown in FIG. 6B,when the first two symbols of the subframe n+1 are used to send thePUSCH, in an SRS coverage enhancement scenario, SRS transmission needsto be reserved as far as possible; in addition, a signal carried in thePUSCH is a data signal, and the data signal is of relatively lowimportance. Therefore, PUSCH transmission in the first two symbols ischosen to be dropped. Specifically, the terminal device uses the firsttwo symbols of the subframe n+1 as the guard period used to forbid theterminal device to send an uplink signal.

In the scenario 1, as shown in FIG. 7A, a network device determines aguard period required for retuning by a terminal device, and determinesthat no uplink signal of the terminal device exists in the guard period.Specifically:

The network device determines the guard period for retuning from thefirst resource to the second resource by the terminal device.

For descriptions of the first resource, the second resource, and theguard period, refer to the descriptions in the embodiment shown in FIG.3. Details are not described herein again in this embodiment of thisapplication.

S702. The network device determines that no uplink signal of theterminal device exists in the guard period.

In a possible design, before the terminal device determines, in thefirst subframe and/or the second subframe, the guard period for retuningin step S302, the method may further include:

receiving, by the terminal device, first indication information sent bythe network device, where the first indication information is used toinstruct the terminal device to determine the guard period in the firstsubframe and/or the second subframe.

Specifically, the network device may send the first indicationinformation to the terminal device after determining the guard periodfor retuning from the first resource to the second resource by theterminal device in step S701. For details, refer to FIG. 7B.

S710. The network device determines the guard period for retuning fromthe first resource to the second resource by the terminal device.

S720. The network device sends the first indication information to theterminal device.

S730, The terminal device determines the first resource and the secondresource after the terminal device receives the first indicationinformation sent by the network device.

S740. The terminal device determines, in the first subframe and/or thesecond subframe, the guard period for retuning.

The first indication information is used to instruct the terminal deviceto determine the guard period by using the solution provided in thisapplication, that is, determine the guard period in a manner ofpreferentially reserving SRS transmission.

Optionally, when the network device sends the first indicationinformation to the terminal device, specifically, the network device mayadd the first indication information to radio resource control (RRC)signaling, and send the signaling to the terminal device; or whensending downlink control information (DCI) to the terminal device, thenetwork device may add the first indication information to the DCI, andsend the DCI to the terminal device.

Specifically, the first indication information is used to indicate thatthe guard period is in the first symbol in a plurality of consecutivesymbols in the second subframe that are used to send the physical uplinkshared channel or the physical uplink control channel.

Alternatively, the first indication information is used to indicate thatthe guard period is in the last symbol of the first subframe and thefirst symbol in a plurality of symbols in the second subframe that areused by the terminal device to send the physical uplink control channel.

Alternatively, the first indication information is used to indicate thatthe guard period is in the first two symbols in a plurality of symbolsin the second subframe that are used by the terminal device to send thephysical uplink shared channel.

Optionally, the network device may send second indication information tothe terminal device. The second indication information is used toinstruct the terminal device to determine the guard period by using asolution provided in the prior art, that is, determine the guard periodin a manner of preferentially dropping SRS transmission. In this case,after receiving the second indication information, the terminal devicedetermines the guard period in the manner of preferentially dropping SRStransmission.

Specifically, the second indication information may be used to indicatethat the guard period is in the last symbol of the first subframe; or ifthe sounding reference signal is sent only in the last symbol of thefirst subframe, the second indication information is used to indicatethat the guard period is in the last symbol of the first subframe andthe first symbol of the second subframe; or if the sounding referencesignal is sent only in at least two symbols of the first subframe, andthe at least two symbols include the last symbol of the first subframe,the second indication information is used to indicate that the guardperiod is in a plurality of consecutive symbols from the first symbol tothe last symbol in the at least two symbols of the first subframe.

A minimum size of a field (indication bit) occupied by the firstindication information or the second indication information may be onebit. For example, the indication bit may be referred to as a flag.Flag=1 indicates the first indication information used to instruct todetermine the guard period in the manner of preferentially reserving theSRS transmission. Flag=0 indicates the second indication informationused to instruct to determine the guard period in the manner ofpreferentially dropping SRS transmission. Alternatively, flag=1 mayindicate the second indication information, and flag=0 may indicate thefirst indication information. This is not specifically limited in thisembodiment of this application. In addition, the size of the fieldoccupied by the indication information and a flag of the indication bitare not specifically limited in this embodiment of this application.

For example, two symbols are required for retuning by the terminaldevice, and the PUCCH is sent in the second subframe. The terminaldevice sends at least two SRSs in the first subframe. As shown in FIG.8, flag=1 indicates the first indication information used to instruct todetermine the guard period in the manner of preferentially reserving theSRS transmission. Flag=0 indicates the second indication informationused to instruct to determine the guard period in the manner ofpreferentially dropping SRS transmission. In FIG. 8, a subframe nindicates the first subframe, and a subframe n+1 indicates the secondsubframe. The SRS is sent in the last two symbols of the subframe n.Because two symbols are required for retuning by the terminal device,when flag=0, the terminal device sends no uplink signal in the last twosymbols of the subframe n. In other words, the last two symbols of thesubframe n are used as the guard period. When flag=1, transmission inone symbol selected from symbols used to transmit the SRS andtransmission in one symbol selected from symbols used to transmit thePUCCH are dropped. Specifically, the terminal device uses the lastsymbol of the subframe n and the first symbol of the subframe n+1 as theguard period used to forbid the terminal device to send an uplinksignal.

In the foregoing implementation, the indication information is carriedin higher layer signaling to indicate a manner in which the terminaldevice performs retuning, so that a symbol in which transmission needsto be reserved by the terminal device during retuning and a symbol inwhich transmission needs to be dropped by the terminal device duringretuning are flexibly selected. This improves flexibility.

Based on the scenario 2, an embodiment of this application provides aretuning method. As shown in FIG. 9, the method includes the followingsteps.

S901. A terminal device determines a first resource and a secondresource.

The first resource is used to receive a physical downlink controlchannel or a physical downlink shared channel. The first resource isdetermined based on a first frequency domain resource and M consecutivesymbols of a downlink pilot timeslot in a special subframe. The secondresource is used to send a sounding reference signal. The secondresource is determined based on a second frequency domain resource andan uplink pilot timeslot in the special subframe. All or a part of thesecond frequency domain resource is not in the first frequency domainresource.

It should be noted. that all or a part of the first frequency domainresource is not in the second frequency domain resource, or the firstfrequency domain resource does not fully overlap with the secondfrequency domain resource.

That the first frequency domain resource does not fully overlap with thesecond frequency domain resource means that no overlapping part existsbetween a subcarrier range within which the first frequency domainresource falls and a subcarrier range within which the second frequencydomain resource falls, or both an overlapping part and a non-overlappingpart exist between a subcarrier range within which the first frequencydomain resource falls and a subcarrier range within which the secondfrequency domain resource falls.

S902. The terminal device determines, in the last N consecutive symbolsof the downlink pilot timeslot or in the uplink pilot timeslot, a guardperiod for retuning.

The guard period is used to forbid the terminal device toreceive/transmit a signal in the guard period. Both M and N are positiveintegers, and M is greater than or equal to N.

Optionally, the terminal device determines, in the last N consecutivesymbols of the downlink pilot timeslot or in the uplink pilot timeslotbased on a retuning capability of the terminal device, the guard periodfor retuning. The retuning capability of the terminal device may bespecifically a quantity of symbols required for retuning by the terminaldevice.

In this embodiment of this application, bandwidth of the first frequencydomain resource is equal to transmission bandwidth of the soundingreference signal, and the second frequency domain resource may be anarrowband resource. Bandwidth of the narrowband resource is equal tomaximum bandwidth that can be supported by the terminal device, orbandwidth of the narrowband resource is equal to a maximum quantity ofphysical resource blocks that can be supported by the terminal device.

The narrowband resource is described with respect to system bandwidth.When UE capabilities are limited, for example, costs are limited andpower consumption is limited, the second frequency domain resource maybe the narrowband resource. Supporting larger bandwidth requires highercosts and higher power consumption. Therefore, using the narrowbandresource can effectively reduce costs and total power consumption,improve transmit power in a unit frequency band to extend an uplinkcoverage area, and so on.

For example, if two symbols are required for retuning by the terminaldevice, when the terminal device determines, in the last N consecutivesymbols of the downlink pilot timeslot, the guard period for retuning,the terminal device determines that the last two symbols of the downlinkpilot timeslot are the guard period for retuning. As shown in FIG. 10, asignal that needs to be received by the terminal device in the DwPTS isthe PDCCH or the PDSCH, and the terminal device transmits the SRS in thelast two symbols of the UpPTS. Therefore, the terminal device does notreceive the PUCCH or the PUSCH in the last two symbols of the DwPTS,uses the last two symbols of the DwPTS as the guard period, and normallytransmits the SRS in the last two symbols of the UpPTS, to ensure SRScoverage enhancement.

In the scenario 2, as shown in FIG. 11A, a network device determines aguard period required for retuning by a terminal device, and determinesthat no signal of the terminal device exists in the guard period.Specifically:

S1101. The network device determines the guard period for retuning fromthe first resource to the second resource by the terminal device.

For descriptions of the first resource, the second resource, and theguard period, refer to the descriptions in the embodiment shown in FIG.9. Details are not described herein again in this embodiment of thisapplication.

S1102. The network device determines that no signal of the terminaldevice exists in the guard period.

In a possible design, before the terminal device determines, in the lastN consecutive symbols of the downlink pilot timeslot, the guard periodfor retuning in step S902, the method may further include:

sending, by the network device, first indication information to theterminal device, where the first indication information is used toinstruct the terminal device to determine the guard period in the last Nconsecutive symbols of the downlink pilot timeslot.

Then, the terminal device receives the first indication information sentby the network device, and determines the guard period based on thefirst indication information.

Specifically, the network device may send the first indicationinformation to the terminal device after determining the guard periodfor retuning from the first resource to the second resource by theterminal device in step S1101. For details, refer to FIG. 11B.

S1110. The network device determines the guard period for retuning fromthe first resource to the second resource by the terminal device.

S1120. The network device sends the first indication information to theterminal device.

S1130. The terminal device determines the first resource and the secondresource after the terminal device receives the first indicationinformation sent by the network device.

S1140. The terminal device determines, in the last N consecutive symbolsof the downlink pilot timeslot based on the first indicationinformation, the guard period for retuning.

The first indication information is used to instruct the terminal deviceto determine the guard period by using the solution provided in thisapplication, that is, determine the guard period in a manner ofreserving SRS transmission.

Optionally, when the network device sends the first indicationinformation to the terminal device, specifically, the network device mayadd the first indication information to RRC signaling, and send thesignaling to the terminal device; or when sending DCI to the terminaldevice, the network device may add the first indication information tothe DCI, and send the DCI to the terminal device.

Optionally, the network device may send second indication information tothe terminal device. The second indication information is used toinstruct the terminal device to determine the guard period by using asolution provided in the prior art, that is, determine the guard periodin a manner of dropping SRS transmission. In this case, after receivingthe second indication information, the terminal device determines theguard period in the manner of dropping SRS transmission.

Specifically, before the terminal device determines, in the uplink pilottimeslot, the guard period for retuning, the network device sends thesecond indication information to the terminal device. Then, the terminaldevice receives the second indication information. The second indicationinformation is used to indicate that the guard period is in the uplinkpilot timeslot.

If the sounding reference signal is sent only in one symbol of theuplink pilot timeslot, the second indication information is used toindicate that the guard period is in the symbol of the uplink pilottimeslot.

Alternatively, if the sounding reference signal is sent in at least twosymbols of the uplink pilot timeslot, the second indication informationis used to indicate that the guard period is in a plurality ofconsecutive signals from the first symbol to the last symbol in the atleast two symbols of the uplink pilot timeslot.

A minimum size of a field (indication bit) occupied by the firstindication information or the second indication information may be onebit. For example, the indication bit may be referred to as a flag.Flag=1 indicates the first indication information used to instruct todetermine the guard period in the manner of preferentially reserving theSRS transmission. Flag=0 indicates the second indication informationused to instruct to determine the guard period in the manner ofpreferentially dropping SRS transmission. Alternatively, flag=1 mayindicate the second indication information, and flag=0 may indicate thefirst indication information. This is not specifically limited in thisembodiment of this application. In addition, the size of the fieldoccupied by the indication information and a flag of the indication bitare not specifically limited in this embodiment of this application.

Based on a same inventive concept as the embodiment corresponding to themethod provided in the scenario 1, an embodiment of this applicationfurther provides a retuning apparatus. The apparatus is applied to aterminal device. As shown in FIG. 12, the apparatus includes:

a first determining module 1201, configured to determine a firstresource and a second resource, where the first resource is used to senda sounding reference signal, the first resource is determined based on afirst frequency domain resource and at least one symbol of a firstsubframe, and the at least one symbol includes the last symbol of thefirst subframe; the second resource is used to send a physical uplinkshared channel or a physical uplink control channel, the second resourceis determined based on a second frequency domain resource and a secondsubframe, and all or a part of the first frequency domain resource isnot in the second frequency domain resource; and the first subframe isthe first subframe in two consecutive subframes, and the second subframeis the second subframe in the two consecutive subframes; and a seconddetermining module 1202, configured to determine, in the first subframeand/or the second subframe, a guard period for retuning, where the guardperiod is used to forbid the terminal device to send an uplink signal inthe guard period.

In a possible design, the second determining module 1202 is specificallyconfigured to determine that the guard period is in the first symbol ina plurality of symbols in the second subframe that are used to send thephysical uplink shared channel or the physical uplink control channel.

In a possible design, if the second resource is used to send thephysical uplink control channel, the second determining module 1202 isspecifically configured to determine that the guard period is in thelast symbol of the first subframe and the first symbol in a plurality ofsymbols in the second subframe that are used to send the physical uplinkcontrol channel.

In a possible design, if the second resource is used to send thephysical uplink shared channel, the second determining module 1202 isspecifically configured to determine that the guard period is in thefirst two symbols in a plurality of consecutive symbols in the secondsubframe that are used to send the physical uplink shared channel.

In a possible design, the apparatus further includes:

a receiving module 1203, configured to receive first indicationinformation before the second determining module 1202 determines, in thefirst subframe and/or the second subframe, the guard period forretuning, where the first indication information is used to instruct theterminal device to determine the guard period in the first subframeand/or the second subframe.

In a possible design, the receiving module 1203 is specificallyconfigured to:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the first indication information; or receivedownlink control information, where the downlink control informationincludes the first indication information.

In a possible design, the apparatus further includes:

a receiving module 1203, configured to receive second indicationinformation before the second determining module 1202 determines theguard period in the first subframe and/or the second subframe.

The second indication information is used to indicate that the guardperiod is in the last symbol of the first subframe or if the soundingreference signal is sent only in the last symbol of the first subframe,the second indication information is used to indicate that the guardperiod is in the last symbol of the first subframe and the first symbolof the second subframe; or if the sounding reference signal is sent onlyin at least two symbols of the first subframe, and the at least twosymbols include the last symbol of the first subframe, the secondindication information is used to indicate that the guard period is in aplurality of consecutive symbols from the first symbol to the lastsymbol in the at least two symbols of the first subframe.

In a possible design, the receiving module 1203 is specificallyconfigured to:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the second indication information; or receivedownlink control information, where the downlink control informationincludes the second indication information.

In a possible design, bandwidth of the first frequency domain resourceis equal to transmission bandwidth of the sounding reference signal, andthe second frequency domain resource is a narrowband resource.

In a possible design, bandwidth of the narrowband resource is equal tomaximum bandwidth that can be supported by the terminal device, orbandwidth of the narrowband resource is equal to a maximum quantity ofphysical resource blocks that can be supported by the terminal device.

In a possible design, the terminal device is a bandwidth-reducedlow-complexity (BL) terminal, a coverage enhanced (CE) terminal, or amachine type communication (MTC) terminal.

Based on a same inventive concept as the embodiment corresponding to themethod provided in the scenario 2, an embodiment of this applicationfurther provides a retuning apparatus. The apparatus is applied to aterminal device. As shown in FIG. 13, the apparatus includes:

a first determining module 1301, configured to determine a firstresource and a second resource, where the first resource is used toreceive a physical downlink control channel or a physical downlinkshared channel, and the first resource is determined based on a firstfrequency domain resource and M consecutive symbols of a downlink pilottimeslot in a special subframe; and the second resource is used to senda sounding reference signal, the second resource is determined based ona second frequency domain resource and an uplink pilot timeslot in thespecial subframe, and all or a part of the second frequency domainresource is not in the first frequency domain resource; and

a second determining module 1302, configured to determine, in the last Nconsecutive symbols of the downlink pilot timeslot or in the uplinkpilot timeslot, a guard period for retuning, where the guard period isused to forbid the terminal device to transmit/receive a signal in theguard period, both M and N are positive integers, and M is greater thanor equal to N.

In a possible design, the apparatus further includes:

a receiving module 1303, configured to receive first indicationinformation before the second determining module 1302 determines, in thelast N consecutive symbols of the downlink pilot timeslot, the guardperiod for retuning, where the first indication information is used toinstruct the terminal device to determine the guard period in the last Nconsecutive symbols of the downlink pilot timeslot.

In a possible design, the receiving module 1303 is specificallyconfigured to:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the first indication information; or receivedownlink control information, where the downlink control informationincludes the first indication information.

In a possible design, the apparatus further includes:

a receiving module 1303, configured to receive second indicationinformation before the second determining module 1302 determines, in theuplink pilot timeslot, the guard period for retuning.

The second indication information is used to indicate that the guardperiod is in the uplink pilot timeslot.

In a possible design, the receiving module 1303 is specificallyconfigured to:

receive radio resource control signaling, where the radio resourcecontrol signaling carries the second indication information; or receivedownlink control information, where the downlink control informationincludes the second indication information.

In a possible design, the first frequency domain resource is anarrowband resource, and bandwidth of the second frequency domainresource is equal to transmission bandwidth of the sounding referencesignal.

In a possible design, bandwidth of the narrowband resource is equal tomaximum bandwidth that can be supported by the terminal device, orbandwidth of the narrowband resource is equal to a maximum quantity ofphysical resource blocks that can be supported by the terminal device.

In a possible design, the terminal device is a bandwidth-reducedlow-complexity (BL) terminal device, a coverage enhanced (CE) terminaldevice, or a machine type communication (MTC) terminal device.

Module division in the embodiments of this application is an example, ismerely logical function division, and may be other division duringactual implementation. In addition, functional modules in theembodiments of this application may be integrated into one processor, ormay exist alone physically, or two or more modules may be integratedinto one module. The integrated module may be implemented in a form ofhardware, or may be implemented in a form of a software functionalmodule.

As shown in FIG. 14, a terminal device may include a processor 1420.Hardware of entities corresponding to the modules shown in FIG. 12 orFIG. 13 may be the processor 1420. The processor 1420 may be a centralprocessing unit (CPU), a digital processing module, or the like. Theterminal device may further include a transceiver 1410. The processor1420 receives data and a message by using the transceiver 1410. Theterminal device may further include a memory 1430, configured to store aprogram to be executed by the processor 1420. The memory 1430 may be anonvolatile memory such as a hard disk (HDD) or a solid-state drive(SSD), or may be a volatile memory such as a random access memory (RAM).The memory 1430 is any other medium that can be configured to carry orstore desired program code in a form of an instruction or a datastructure and that can be accessed by a computer, but is not limitedthereto.

The processor 1420 is configured to execute the program code stored inthe memory 1430, and is specifically configured to perform the methodsperformed by the terminal device in the embodiments shown in FIG. 3 toFIG. 11. For details, refer to the method implementation described inthe embodiments shown in FIG. 3 to FIG. 11. The details are notdescribed herein again in this application.

A specific connection medium between the transceiver 1410, the processor1420, and the memory 1430 is not limited in this embodiment of thisapplication. In this embodiment of this application, the memory 1430,the processor 1420, and the transceiver 1410 are connected by using abus 1440 in FIG. 14. The bus is represented by using a bold line in FIG.14. A manner of connection between other components is merely an examplefor description, and imposes no limitation. The bus may be classifiedinto an address bus, a data bus, a control bus, and the like. For easeof representation, only one bold line is used in FIG. 14 to representthe bus, but it does not indicate that there is only one bus or one typeof bus.

Based on a same inventive concept as the embodiment corresponding to themethod provided in the scenario 1, an embodiment of this applicationprovides a retuning apparatus. The apparatus is applied to a networkdevice. As shown in FIG. 15, the apparatus includes:

a first determining module 1501, configured to determine a guard periodfor retuning from a first resource to a second resource by a terminaldevice, where the guard period is in a first subframe and/or a secondsubframe, the guard period is used to forbid the terminal device to sendan uplink signal in the guard period, the first resource is used by theterminal device to send a sounding reference signal, the first resourceis determined based on a first frequency domain resource and at leastone symbol of the first subframe, and the at least one symbol includesthe last symbol of the first subframe; the second resource is used bythe terminal device to send a physical uplink control channel or aphysical uplink shared channel, the second resource is determined basedon a second frequency domain resource and the second subframe, and allor a part of the first frequency domain resource is not in the secondfrequency domain resource; and the first subframe is the first subframein two consecutive subframes, and the second subframe is the secondsubframe in the two consecutive subframes; and a second determiningmodule 1502, configured to determine that no uplink signal of theterminal device exists in the guard period.

In a possible design, the apparatus further includes:

a sending module 1503, configured to send first indication informationto the terminal device, where the first indication information is usedto indicate that the guard period is in the first subframe and/or thesecond subframe.

In a possible design, the first indication information is used toindicate that the guard period is in the first symbol in a plurality ofconsecutive symbols in the second subframe that are used to send thephysical uplink shared channel or the physical uplink control channel.

In a possible design, the first indication information is used toindicate that the guard period is in the last symbol of the firstsubframe and the first symbol in a plurality of symbols in the secondsubframe that are used by the terminal device to send the physicaluplink control channel.

In a possible design, the first indication information is used toindicate that the guard period is in the first two symbols in aplurality of symbols in the second subframe that are used by theterminal device to send the physical uplink shared channel.

In a possible design, the sending module 1503 is specifically configuredto:

send radio resource control signaling to the terminal device, where theradio resource control signaling carries the first indicationinformation; or send downlink control information to the terminaldevice, where the downlink control information includes the firstindication information.

In a possible design, the apparatus further includes:

a sending module 1503, configured to send second indication informationto the terminal device.

The second indication information is used to instruct the terminaldevice to generate the guard period in the last symbol of the firstsubframe; or if the sounding reference signal is sent only in the lastsymbol of the first subframe, the second indication information is usedto indicate that the guard period is in the last symbol of the firstsubframe and the first symbol of the second subframe; or if the soundingreference signal is sent in at least two consecutive symbols of thefirst subframe, and the at least two consecutive symbols include thelast two symbols of the first subframe, the second indicationinformation is used to indicate that the guard period is in the last twosymbols of the first subframe.

In a possible design, the sending module 1503 is specifically configuredto:

send radio resource control signaling to the terminal device, where theradio resource control signaling carries the second indicationinformation; or send downlink control information to the terminaldevice, where the downlink control information includes the secondindication information.

Based on a same inventive concept as the embodiment corresponding to themethod provided in the scenario 2, an embodiment of this applicationprovides a retuning apparatus. The apparatus is applied to a networkdevice. As shown in FIG. 16, the apparatus includes:

a first determining module 1601, configured to determine a guard periodfor retuning from a first resource to a second resource by a terminaldevice, where the guard period is in the last N consecutive symbols of adownlink pilot timeslot in a special subframe or the guard period is inan uplink pilot timeslot, and the guard period is used to forbid theterminal device to transmit/receive a signal in the guard period: thefirst resource is used to receive a physical downlink control channel ora physical downlink shared channel, and the first resource is determinedbased on a first frequency domain resource and M consecutive symbols ofthe downlink pilot timeslot; the second resource is used to send asounding reference signal, the second resource is determined based on asecond frequency domain resource and the uplink pilot timeslot in thespecial subframe, and all or a part of the second frequency domainresource is not in the first frequency domain resource and both M and Nare positive integers, and M is greater than or equal to N; and

a second determining module 1602, configured to determine that no signalof the terminal device exists in the guard period.

In a possible design, the apparatus further includes:

a sending module 1603, configured to send indication information to theterminal device, where the indication information is used to indicatethat the guard period is in the last N consecutive symbols of thedownlink pilot timeslot or indicate that the guard period is in theuplink pilot timeslot.

In a possible design, the sending module 1603 is specifically configuredto:

send radio resource control signaling to the terminal device, where theradio resource control signaling carries the indication information; orsend downlink control information to the terminal device, where thedownlink control information includes the indication information.

Module division in the embodiments of this application is an example, ismerely logical function division, and may be other division duringactual implementation. In addition, functional modules in theembodiments of this application may be integrated into one processor, ormay exist alone physically, or two or more modules may be integratedinto one module. The integrated module may be implemented in a form ofhardware, or may be implemented in a form of a software functionalmodule.

As shown in FIG. 17, a network device may include a processor 1720.Hardware of entities corresponding to the modules shown in FIG. 15 orFIG. 16 may be the processor 1720. The processor 1720 may be a CPU, adigital processing module, or the like. The network device may furtherinclude a transceiver 1710. The processor 1720 receives data and amessage by using the transceiver 1710. The network device may furtherinclude a memory 1730, configured to store a program to be executed bythe processor 1720, The memory 1730 may be a nonvolatile memory such asan HDD or an SSD, or may be a volatile memory such as a RAM. The memory1730 is and other medium that can be configured to carry or storedesired program code in a form of an instruction or a data structure andthat can be accessed by a computer, but is not limited thereto.

The processor 1720 is configured to execute the program code stored inthe memory 1730, and is specifically configured to perform the methodsperformed by the network device in the embodiments shown in FIG. 3 toFIG. 11. For details, refer to the method implementation described inthe embodiments shown in FIG. 3 to FIG. 11. The details are notdescribed herein again in this application.

A specific connection medium between the transceiver 1710, the processor1720, and the memory 1730 is not limited in this embodiment of thisapplication, in this embodiment of this application, the memory 1730,the processor 1720, and the transceiver 1710 are connected by using abus 1740 in FIG. 17. The bus is represented by using a bold line in FIG.17. A manner of connection between other components is merely an examplefor description, and imposes no limitation. The bus may be classifiedinto an address bus, a data bus, a control bus, and the like. For easeof representation, only one bold line is used in FIG. 17 to representthe bus, but it does not indicate that there is only one bus or one typeof bus.

In the embodiments of this application, SRS sending is notpreferentially dropped. Instead, SRS transmission is chosen to bepreferentially reserved. Transmission of a signal less important thanthe SRS is preferentially dropped, to enhance SRS coverage based onterminal retuning. In addition, the network device instructs, by usinghigher layer signaling, the terminal device to preferentially drop SRStransmission or preferentially reserve SRS transmission. This improvessymbol dropping and reserving flexibility during retuning.

A person skilled in the art should understand that the embodiments ofthis application may be provided as a method, a system, or a computerprogram product. Therefore, this application may use a form of hardwareonly embodiments, software only embodiments, or embodiments with acombination of software and hardware. Moreover, this application may usea form of a computer program product that is implemented on one or morecomputer-usable storage media (including but not limited to a magneticdisk storage, a CD-ROM, an optical memory, and the like) that includecomputer-usable program code.

This application is described with reference to the flowcharts and/orblock diagrams of the method, the device system), and the computerprogram product according to the embodiments of this application. Itshould be understood that computer program instructions may be used toimplement each process and/or each block in the flowcharts and/or theblock diagrams, and a combination of a process and/or a block in theflowcharts andlor the block diagrams. These computer programinstructions may be provided to a general-purpose computer, a dedicatedcomputer, an embedded processor, or a processor of another programmabledata processing device to generate a machine, so that the instructionsexecuted by a computer or a processor of another programmable dataprocessing device generate an apparatus for implementing a specifiedfunction in one or more processes in the flowcharts and/or in one ormore blocks in the block diagrams.

These computer program instructions may be stored in a computer readablememory that can instruct a computer or another programmable dataprocessing device to work in a specific manner, so that the instructionsstored in the computer readable memory generate an artifact thatincludes an instruction apparatus. The instruction apparatus implementsa specified function in one or more processes in the flowcharts and/orin one or more blocks in the block diagrams.

These computer program instructions may alternatively be loaded onto acomputer or another programmable data processing device, so that aseries of operations and steps are performed on the computer or theanother programmable device, thereby generating computer-implementedprocessing. Therefore, the instructions executed on the computer or theanother programmable device provide steps for implementing a specifiedfunction in one or more processes in the flowcharts and/or in one ormore blocks in the block diagrams.

Obviously, a person skilled in the art can make various modificationsand variations to the embodiments of this application without departingfrom the spirit and scope of the embodiments of this application. Thisapplication is intended to cover these modifications and variationsprovided that they fall within the scope of protection defined by theclaims of this application and their equivalent technologies.

1. A retuning method, comprising: determining, by a terminal device, afirst resource and a second resource, wherein the first resource is usedto receive a physical downlink control channel or a physical downlinkshared channel, wherein the first resource is determined based on afirst frequency domain resource and M consecutive symbols of a downlinkpilot timeslot in a special subframe, wherein the second resource isused to send a sounding reference signal, wherein the second resource isdetermined based on a second frequency domain resource and an uplinkpilot timeslot in the special subframe, and wherein all or a part of thesecond frequency domain resource is not in the first frequency domainresource; and determining, by the terminal device in the last Nconsecutive symbols of the downlink pilot timeslot, a guard period forretuning, wherein the guard period is used to forbid the terminal deviceto transmit or receive a signal in the guard period, wherein both M andN are positive integers, and wherein M is greater than or equal to N. 2.The method according to claim 1, before the determining, by the terminaldevice in the last N consecutive symbols of the downlink pilot timeslot,a guard period for retuning, further comprising: receiving, by theterminal device, first indication information, wherein the firstindication information is used to indicate the terminal device todetermine the guard period in the last N consecutive symbols of thedownlink pilot timeslot.
 3. The method according to claim 2, wherein thereceiving, by the terminal device, first indication informationcomprises: receiving, by the terminal device, radio resource controlsignaling, wherein the radio resource control signaling carries thefirst indication information.
 4. The method according to claim 1,wherein the first frequency domain resource is a narrowband resource,and wherein bandwidth of the second frequency domain resource is equalto transmission bandwidth of the sounding reference signal.
 5. Themethod according to claim 1, wherein the terminal device is abandwidth-reduced low-complexity (BL) terminal device, a coverageenhanced (CE) terminal device, or a machine type communication (MTC)terminal device.
 6. A retuning method, comprising: determining, by anetwork device, a guard period for retuning from a first resource to asecond resource by a terminal device, wherein the guard period is in thelast N consecutive symbols of a downlink pilot timeslot in a specialsubframe, wherein the guard period is used to forbid the terminal deviceto transmit or receive a signal in the guard period, wherein the firstresource is used to send a physical downlink control channel or aphysical downlink shared channel, wherein the first resource isdetermined based on a first frequency domain resource and M consecutivesymbols of the downlink pilot timeslot, wherein the second resource isused to receive a sounding reference signal, the second resource isdetermined based on a second frequency domain resource and an uplinkpilot timeslot in the special subframe, wherein all or a part of thesecond frequency domain resource is not in the first frequency domainresource, wherein both M and N are positive integers, and wherein M isgreater than or equal to N; and determining, by the network device, thatno signal of the terminal device exists in the guard period.
 7. Themethod according to claim 6, wherein the method further comprises:sending, by the network device, indication information to the terminaldevice, wherein the indication information is used to indicate that theguard period is in the last N consecutive symbols of the downlink pilottimeslot.
 8. The method according to claim 7, wherein the sending, bythe network device, indication information to the terminal devicecomprises: sending, by the network device, radio resource controlsignaling to the terminal device, wherein the radio resource controlsignaling carries the indication information.
 9. The method according toclaim 6, wherein the first frequency domain resource is a narrowbandresource, and wherein bandwidth of the second frequency domain resourceis equal to transmission bandwidth of the sounding reference signal. 10.A retuning apparatus, comprising: a memory storing program instructions;and at least one processor coupled to the memory, wherein the programinstructions, when executed by the at least one processor, cause theapparatus to: determine a first resource and a second resource, whereinthe first resource is used to receive a physical downlink controlchannel or a physical downlink shared channel, wherein the firstresource is determined based on a first frequency domain resource and Mconsecutive symbols of a downlink pilot timeslot in a special subframe,wherein the second resource is used to send a sounding reference signal,wherein the second resource is determined based on a second frequencydomain resource and an uplink pilot timeslot in the special subframe,and wherein all or a part of the second frequency domain resource is notin the first frequency domain resource; and determine, in the last Nconsecutive symbols of the downlink pilot timeslot, a guard period forretuning, wherein the guard period is used to forbid the apparatus totransmit or receive a signal in the guard period, wherein both M and Nare positive integers, and wherein M is greater than or equal to N. 11.The apparatus according to claim 10, wherein the program instructions,when executed by the at least one processor, cause the apparatus to:receive first indication information, wherein the first indicationinformation is used to indicate the apparatus to determine the guardperiod in the last N consecutive symbols of the downlink pilot timeslot.12. The apparatus according to claim 11, wherein the programinstructions, when executed by the at least one processor, cause theapparatus to: receive radio resource control signaling, wherein theradio resource control signaling carries the first indicationinformation.
 13. The apparatus according to claim 10, wherein the firstfrequency domain resource is a narrowband resource, and whereinbandwidth of the second frequency domain resource is equal totransmission bandwidth of the sounding reference signal.
 14. Theapparatus according to claim 10, wherein the apparatus is abandwidth-reduced low-complexity (BL) terminal device, a coverageenhanced (CE) terminal device, or a machine type communication (MTC)terminal device.
 15. A network device, comprising: a memory storingprogram instructions; and at least one processor coupled to the memory,wherein the program instructions, when executed by the at least oneprocessor, cause the network device to: determine a guard period forretuning from a first resource to a second resource by a terminaldevice, wherein the guard period is in the last N consecutive symbols ofa downlink pilot timeslot in a special subframe, wherein the guardperiod is used to forbid the terminal device to transmit or receive asignal in the guard period, wherein the first resource is used to send aphysical downlink control channel or a physical downlink shared channel,wherein the first resource is determined based on a first frequencydomain resource and M consecutive symbols of the downlink pilottimeslot, wherein the second resource is used to receive a soundingreference signal, wherein the second resource is determined based on asecond frequency domain resource and an uplink pilot timeslot in thespecial subframe, wherein all or a part of the second frequency domainresource is not in the first frequency domain resource, wherein both Mand N are positive integers, and M is greater than or equal to N; anddetermine that no signal of the terminal device exists in the guardperiod.
 16. The network device according to claim 15, wherein theprogram instructions, when executed by the at least one processor, causethe network device to: send indication information to the terminaldevice, wherein the indication information is used to indicate that theguard period is in the last N consecutive symbols of the downlink pilottimeslot.
 17. The network device according to claim 16, wherein theprogram instructions, when executed by the at least one processor, causethe network device to: send radio resource control signaling to theterminal device, wherein the radio resource control signaling carriesthe indication information.
 18. The network device according to claim15, wherein the first frequency domain resource is a narrowbandresource, and wherein bandwidth of the second frequency domain resourceis equal to transmission bandwidth of the sounding reference signal.